Add debug information to help understand failures finding schemas

[yannh]

When using -schema-location, it is sometimes difficult to understand why kubeconform fails to find the appropriate resource schema. This PR adds a -debug parameter that prints information on where Kubeconform tries to download schemas and which schema it will use for validation.

[yannh]

cc @eyarz I've been wanting this option forever to make it easier to use -schema-location... if there is any additional debug info you think could be useful or any comment on the format now would be a good time :)

[eyarz]

Awesome! More debug info is always good :)
To be frank, we don't see our users having a lot of issues with this flag.

We added the CRDs-catalog to run with default, so basically, Datree users are running:
kubeconform -schema-location default -schema-location [CRDs-catalog path].
This solved 99% of all the issues that our users had when they tried to use the -schema-location flag to validate CRDs.

The debug info level and the format LGTM 👍
Just to make sure, if not using the deug flag, the error could not find schema for... will still be raised, right?
I'm asking because we have some logic that relies on the error message.

[yannh]

Yep that won't change, but you won't always see all the different URLs kubeconform tried to download - when writing tests I sometimes have a hard time myself trying to understand the paths computed...
And yes your CRD-catalog is prettty neat I might start to use it soon as well 🚀